1. Field of the Invention
The present invention relates generally to an image sensor module, and in particular to a contact image sensor module that can be repaired when a substandard product appears and also to a method for repairing and assembling it.
2. The Related Arts
As well known, a contact image sensor (CIS) module is used as a picture image reading means in the scanner, facsimile machine, or the likes. The CIS is located on a rail means of a scanner panel, moves front-and-back and controlled by the rail and mechanical means to reading the original document that is being scanned. The obtained light signals are represented the original document and can be converted into electrical signal that will be translated into electro-image document by the software.
In general, the CIS module comprises a PCB 10, a sensor housing 20, a rod lens 30 and a light emitting diode (LED) source 40, as shown in FIG. 1.
The PCB 10 is formed by bonding photosensor elements and the electronic elements onto a special PCB. The LED source 40 comprises a LED 41 and an optical rod 42.
The CIS module's working theory is described as following paragraph. The CIS illuminates lights from the LED source 40, irradiates the lights onto the original document that is being scanned on a scanner panel, passes the lights reflected from the original document through the rod lens 30, and then transfer onto the photosensor elements, such as Charge-Coupled Device (CCD) or Complementary Metal Oxide Semiconductor (CMOS). The literal and graphic images of the original document are then recorded according to a principle that different intensity of the reflected lights that strike the photosensor elements represent different contents of the scanned document. Finally, the reflected lights will be converted into electrical signals that can be read and translated into digital pixels by the software.
The assembly process of a conventional CIS module used in the scanner generally includes two different periods.
As shown in FIGS. 2a, 2b and 2c, in the first period of the assembly process, the rod lens 30 is fixed into a lens-receiving groove 26 on a second surface 22 of the sensor housing 20. The LED source 40 is located in a light source-receiving groove 27 which extends on the second surface 22. The conductive tails of the LED source 40 pass through the holes 28 from the first surface 21 to the second surface 22 and glued to the sensor housing 20.
In the second period of assembly process, the PCB 10 will be assembled into the sensor housing 20. The prior methods for assembling the PCB 10 into the sensor housing 20 may be separated into two different types.
The first method is shown in FIG. 2c. In firstly, the PCB 10 will be put into the sensor housing 20, and then some tapping screws will pass through the predetermined holes on the PCB 10 and fix the PCB 10 in the sensor housing 20. An advantage of this method is that the assembly process is easily and rapidly. But an obvious disadvantage of this method is that the broken pieces produced by the tapping screws will be more likely to stain photosensor elements located on the PCB 10 and affect signal-receiving capabilities of the photosensor elements. Another disadvantage is that to disassembly or repair the CIS is inconvenient. During the process of disassembling and repairing the CIS, the broken pieces will be produced again and locking ability of tapping screws will be reduced because the tapping screws must be repeatedly screwed on the same positions as former.
The other prior assembly method is shown in FIGS. 3a, 3b and 3c. The sensor housing 20 is manufactured by plastic molding with a plurality of predetermined posts 11 on it. The posts 11 of the sensor housing 20 can pass through the corresponding holes 12 on the PCB 10 and extend outwardly when the PCB 10 is laid on the housing 20. Some fastening means will be formed at the tips of the posts by hot-press machine whereby the PCB 10 is fixed.
Using above method may avoid the problem of the broken pieces, but new question appears. If the assembled CIS is unqualified or has any one of the post 11 is broken during the assembly process, manufacturer must cut off all of the fastening means, disassembly them and try to repair the CIS module. But the PCB 10 can't be fixed to the housing 20 again, because the tips of the post 11 don't exist. As a result, the housing 20 will not be used again and all of the glued optical elements, such as the rod lens 30 and the LED source 40, are useless. It is obvious that the manufacturing cost will rise under this situation.
It is thus desired to provide a new method and structure that overcome the above-mentioned problems in the prior arts.